Well, I made 25k miles last month (I think that is referred to here as 2P?). I thought this would automatically get my default seat assignment into the E+ seats, but it is not so.

I know the trips have to be booked after the UA system recognizes the 25K, and these trips were. However, when I logged on to get my boarding pass the night before, both times I was defaulted to the back of the bus. I had no problem changing seats online to the E+ section (got my own group of three each time - low loads). However, it seems I have to manually do this change - the system does not default me into E+ just because I made 25k.

Is there any setup I can do that will change the default? I'm concerned about getting stuck in the back of the bus one of those times when I don't have a chance to check in online, and get to the airport too late to get a seat assignment from Mr. EZ, and have to get my seat assignment at the gate.

Call the MP desk and have them manually upgrade your status. Should produce desired results.

Sometimes there is a lag between you making MP status and it being recognized by the system. Contact MP and make sure your 2P status has been uploaded and you should be fine going forward.